The goal of the research was to see how tax enforcement and tax penalty affect tax revenue yield in southwest Nigeria. Tax enforcement and tax penalty are both part of the tax administrators’ programs with a view to improve tax generation. Residents have a natural desire to decrease their tax liabilities by overstating their expenses The attitude of taxpayers in Nigeria has not been encouraging overtime. The rate of tax compliance is abysmally low. The research took place in Ekiti, Ondo, Osun, Oyo, Ogun, and Lagos states in southwest Nigeria. The study employed the survey research method, with 302 audit and risk department employees from the State Board of Internal Revenue (SBIR) and the Federal Inland Revenue Service (FIRS) as the study's population. 172 sample size was scientifically obtained through Taro Yamane sampling approach. The researcher devised a closed-ended questionnaire called Tax Administration and Tax Yield (TATY) to collect relevant data for the study. According to the findings, tax enforcement and tax penalty has a significant correlational effect on tax yield in southwest Nigeria, tax administrator should continue to enforce tax laws on taxpayers, and appropriate penalty should be applied consistently on tax defaulters to boost tax generation in the region. Keywords: Tax enforcement, Tax penalty, Tax yield, tax administration, Taxpayers Word Count: 204 DOI: 10.7176/RJFA/13-6-06 Publication date: March 31 st 2022